043
FXUS61 KCTP 081441
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1041 AM EDT THU MAY 8 2025
SYNOPSIS
*SHOWERS AND A COUPLE OF THUNDERSTORMS WITH LOCALLY HEAVY
RAINFALL ACROSS SOUTH CENTRAL PA THIS AFTERNOON AND EVENING
*COOLER END TO THE WEEK WITH PERIODS OF RAIN/SHOWERS FRIDAY
ENDING FROM SOUTHWEST TO NORTHEAST FRIDAY NIGHT-AM SATURDAY
*RAIN-FREE AND PLEASANT CONDITIONS THROUGH MOTHER'S DAY WEEKEND
NEAR TERM /THROUGH TONIGHT/
1030 AM UPDATE... LATE MORNING SATELLITE AND RADAR IMAGERY SHOW
A BAND OF LOWER CLOUDS AND SCATTERED LIGHT SHOWERS ACROSS THE
NORTHERN TIER, LARGELY JUST BEHIND A SLOW MOVING SURFACE FRONTAL
BOUNDARY. GIVEN THE ORIENTATION OF THE BOUNDARY BEING NEARLY
PARALLEL TO THE UPPER-LEVEL FLOW, AS WELL AS THE APPROACH OF AN
UPPER LOW FROM THE TN VALLEY, THIS FRONT IS NOT EXPECTED TO MOVE
MUCH THROUGH THE AFTERNOON. GIVEN THICKER CLOUDS, LOW-LEVEL
NORTHERLY FLOW, AND ASSOCIATED COOL AIR ADVECTION, WE'LL HAVE A
N-S TEMPERATURE GRADIENT ACROSS THE COMMONWEALTH, WHICH IS
PRETTY WELL REFLECTED IN OUR CURRENT MAXIMUM TEMPERATURE GRID.
AS FOR ADDITIONAL CONVECTIVE DEVELOPMENT, WE DO ANTICIPATE THAT
SOME OF THIS WILL OCCUR COINCIDENT WITH PEAK HEATING THIS
AFTERNOON, MAINLY NEAR AND SOUTH OF I-80. MODEST THERMODYNAMICS
(MLCAPE ROUGHLY 300-700 J/KG) AND WEAK DEEP-LAYERED SHEAR (0-6
KM VALUES MOSTLY UNDER 20-25 KT) SHOULD LIMIT THE PROBABILITY
THAT ANY STORMS APPROACH STRONG-SEVERE LEVELS.
AS WE MOVE TOWARDS EARLY EVENING AND UPPER-LEVEL ENERGY
CONTINUES ITS APPROACH FROM THE SOUTHWEST, WE STILL ANTICIPATE A
GENERAL CONVECTIVE TO STRATIFORM LIGHT RAINFALL TRANSITION WITH
TIME.
PREVIOUS DISCUSSION... IR SAT TRENDS SHOW HIGH CLOUDS HAVE
PEELED AWAY ACROSS THE SOUTHERN 3/4 OF THE FORECAST AREA; THIS
IS BULLISH FOR AREAS OF VALLEY FOG TO DEVELOP THROUGH SUNRISE
UNDER MORE IDEAL RADIATIONAL COOLING. THE LATEST OBSERVATIONAL
TRENDS 08-09Z INDICATE A HYBRID FOG/STRATUS PATTERN DEVELOPING
BEHIND THE SFC COLD FRONT OVER THE NORTHERN TIER.
A COMPLEX UPPER-LEVEL EVOLUTION WILL BEGIN TODAY AND PORTEND
MORE WET WX THROUGH THE END OF THE WEEK. A POSITIVELY TILTED
UPPER TROUGH WILL SPLIT/BREAK INTO A COLD CLOSED 500MB LOW BY
TONIGHT OVER WESTERN PA. THIS LARGE SCALE PATTERN TRANSITION
WILL SLOW THE SOUTHEASTWARD PROGRESS OF THE AFOREMENTIONED COLD
FRONT, SETTING UP A TRIGGERING MECHANISM OR FOCUS FOR DIURNAL
CONVECTION ACROSS SOUTH CENTRAL PA THIS AFTERNOON AND EVENING.
THE AIRMASS ALONG AND TO THE SOUTH/EAST OF THE COLD FRONT WILL
BE ONLY MARGINALLY UNSTABLE, BUT FAIRLY MOIST WITH PWS 1-1.25
INCHES OVER THE LOWER SUSQUEHANNA VALLEY. THE 08/00Z HREF PMM
SHOWS THE HIGHEST NEIGHBORHOOD PROBS FOR >1"/3HR ALONG AND TO
THE SOUTHEAST OF I-81. SOIL SENSITIVITY IS RATHER VARIABLE OVER
THIS AREA BASED ON THE ONGOING DROUGHT CONDITIONS AND 3HR FFG
VALUES. THERE IS SOME SPREAD IN THE HIRES QPF AMOUNTS AND
LOCATIONS.
AN ISOLATED SHORT TERM FLOODING RISK WILL REMAIN HIGHLY
DEPENDENT ON EXACTLY WHERE THE HEAVY RAIN FALLS; AREAS THAT HAVE
EXPERIENCED EXCEPTIONALLY HIGH SOIL SATURATION/SENSITIVITY AND
ELEVATED SMALL STREAM FLOWS OVER THE PAST SEVERAL DAYS WOULD BE
MOST AT RISK. ADDITIONAL RAIN IS EXPECTED ACROSS THE SOUTHEAST
HALF OF THE CWA OVERNIGHT INTO EARLY FRIDAY MORNING AS A FRONTAL
WAVE RIDES NORTH ALONG THE QUASI-STATIONARY BOUNDARY.
THE NORTHERN TIER WILL SEE A NOTICEABLE COOL DOWN OF -10
DEGREES VS. YESTERDAY IN BOTH MAX (55-60F) AND MIN TEMPS
(40-45F).
SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/
THE SLOW MOVING, CLOSED 500MB LOW WILL TRACK ALONG THE MD LINE
ON FRIDAY BEFORE REACHING THE NYC AREA BY 12Z SATURDAY. BROAD
SYNOPTIC LIFT AND FGEN/DEFORMATION WILL DRIVE FAIRLY WIDESPREAD
SHOWER ACTIVITY TO END THE WEEK. CLOUDY, COOL AND WET
CONDITIONS ARE EXPECTED OVER MOST OF CPA WITH A ~10F SETBACK IN
DAYTIME HIGHS ACROSS THE BOARD. THIS TRANSLATES TO MAX TEMPS IN
THE 50-65F RANGE OR 10-15F BELOW CLIMO ACROSS THE SOUTHERN 3/4
OF THE CWA. WE WILL NEED TO MONITOR POTENTIAL COMMA HEAD WRAP
AROUND PRECIP WHICH MAY SETUP OVER A LONGER DURATION AND PIVOT
ACROSS THE NORTHEAST ZONES WHICH HAVE SOME OF THE LOWEST FFGS IN
THE CWA. THANKFULLY, IT APPEARS THAT ADDITIONAL RAINFALL ON
FRIDAY WILL BE MORE OF A STEADIER, LIGHT TO MODERATE INTENSITY.
THE LATEST MODEL TIMING IS FOR RAIN TO END FROM SOUTHWEST TO
NORTHEAST BY 12Z SATURDAY AS THE FRONTAL SYSTEM LIFTS AWAY AND
ACCELERATES TO THE NORTHEAST ALONG THE NEW ENGLAND COAST. HIGH
PRESSURE BUILDING INTO CPA WILL PROVIDE A BEAUTIFUL AND RAIN-
FREE START TO MOTHER'S DAY WEEKEND WITH LOW HUMIDITY.
LONG TERM /SUNDAY THROUGH WEDNESDAY/
A REALLY NICE MOTHER'S DAY SHAPING UP ACROSS CPA WITH SUNSHINE
AND WARMER TEMPS IN THE 65-75F RANGE. AS HIGH PRESSURE MOVES
OFF THE EAST COAST MON, RETURN FLOW WILL USHER IN INCREASING
MOISTURE FOR MON-TUE. LONGER RANGE GUIDANCE SUGGESTS A DEEP
LONGWAVE TROUGH IN THE SOUTHERN BRANCH OF THE JET STREAM THAT
MAY BRING UNSETTLED WEATHER ONCE AGAIN BY NEXT WEEK.
AVIATION /15Z THURSDAY THROUGH MONDAY/
UNDER LIGHT WINDS AND CLEAR SKIES SOME POCKETS OF FOG ARE STILL
POSSIBLE THIS MORNING, ESPECIALLY ACROSS THE NORTH AND WEST
AIRFIELDS, JST, AOO, BFD. WIDESPREAD COVERAGE IS NOT
ANTICIPATED BUT QUICK AND SHORT LIVE DROP IS VSBY AROUND
SUNRISE IS POSSIBLE. VSBY IS EXPECTED TO IMPROVE BETWEEN
12-14Z THU.
LAYERED STRATUS AND STRATOCU WILL SPREAD EAST ACROSS THE REGION
DURING THE LATE MORNING (NW) THROUGH MID HOURS (SE) WITH
SHOWERS AND PERHAPS TSRA IN THE AFTERNOON (MAINLY ACROSS THE SE
HALF OF PA). CIGS UNDER A LIGHT NORTHERLY FLOW COULD DIP
INTO/OR STAY IN THE IFR TO LOW IFR RANGE FOR THE LATE MORNING
AND EARLY AFTERNOON AT KBFD AND KJST, WHILE OTHER AIRFIELDS IN
THE CENTRAL RIDGE AND VALLEY REGION WILL DEAL WITH MAINLY
PERIODS OF MVFR OR LOW END VFR CIGS THROUGH THE DAY THURSDAY
ALONG WITH A RELATIVELY LIGHT NORTH TO NNE BREEZE. RESTRICTIONS
IN PERIODS OF RAIN ARE POSSIBLE THU NIGHT INTO THE FIRST HALF OF
FRI, WITH IMPROVEMENT FROM NW TO SE LATER FRI.
OUTLOOK...
SAT-MON...NO SIG WX.
MON...SLGT CHC -SHRA ACROSS THE SOUTH
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...STEINBUGL
NEAR TERM...JUREWICZ/STEINBUGL
SHORT TERM...STEINBUGL
LONG TERM...COLBERT/BAUCO
AVIATION...GARTNER/COLBERT
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